1. Field of the Invention
The present invention relates to a radiation image capturing system and a radiation image capturing apparatus.
2. Description of Related Art
There has been developed various types of so-called direct-type radiation image capturing apparatuses and so-called indirect-type radiation image capturing apparatuses. The direct-type radiation image capturing apparatus is a type that generates electric charges by detection elements according to the radiation exposure dose such as x-ray and converts the generated electric charges to electric signals. The indirect-type radiation image capturing apparatus is a type that converts the irradiated radiation to electromagnetic waves of other wavelength such as visible light by a scintillator or the like, and thereafter, generates electric charges by photoelectric conversion elements such as photodiodes according to the energy of the electromagnetic waves which are converted and irradiated and converts the generated electric charges to electric signals (that is, image data). In the present invention, the detection elements in the direct-type radiation image capturing apparatus and the photoelectric conversion elements in the indirect-type radiation image capturing apparatus are called radiation detection elements all together.
Such types of radiation image capturing apparatuses are known as FPD (Flat Panel Detector), and conventionally, they are configured as so-called exclusive type in which an image capturing apparatus is integrally formed with a support platform (for example, see Japanese Patent Laid-Open Publication No. H9-73144). However, in recent years, a portable radiation image capturing apparatus which is made to be portable by placing the radiation detection elements and the like in a housing is developed and is being put to practical use (for example, see Japanese Patent Laid-Open Publication No. 2006-058124 and Japanese Patent Laid-Open Publication No. H6-342099).
Such radiation image capturing apparatus is usually configured so that a plurality of radiation detection elements 7 are two dimensionally arranged (matrix form) on a detection part P and each of the radiation detection elements 7 is connected to a switch unit formed of a Thin Film Transistor (hereinafter, called TFT) 8, as shown in the after-mentioned FIG. 7 and others, for example.
Then, in radiation image capturing, a radiation source of a radiation generation apparatus emits radiation onto the radiation image capturing apparatus via the target body. The electric charges accumulated in the radiation detection elements 7 by the radiation irradiation are released to signal lines 6 sequentially and converted into image data to be read out.
In conventional radiation image capturing apparatuses, as after-mentioned, ON voltage is applied to scanning lines 5 sequentially and reset processing is performed on each of the radiation detection elements 7 before radiation image capturing is performed (see after-mentioned FIG. 13). Then, when an exposure switch 56 of the radiation generation apparatus 55 (see after-mentioned FIGS. 11 and 12) is operated by a radiation technologist to perform radiation irradiation, as shown in after-mentioned FIG. 14, a radiation irradiation start signal is sent from the radiation generation apparatus 55 to the radiation image capturing apparatus.
At the time when the radiation image capturing apparatus ends the reset processing Rm for one frame, the radiation image capturing apparatus switches to an electric charge accumulating state and sends an interlock release signal to the radiation generation apparatus 55. Then, the radiation generation apparatus 55 emits radiation from the radiation source 52 only after receiving the interlock release signal. In many cases, radiation image capturing has been performed in such way.
The flow of these processing will be described in detail below. Also, hereinafter, the method of performing radiation image capturing by exchanging signals between the radiation image capturing apparatus and the radiation generation apparatus and by the radiation image capturing apparatus and the radiation generation apparatus cooperating with each other in such way will be called the cooperation method.
Incidentally, when manufacturers are different between the radiation image capturing apparatus and the radiation generation apparatus, it is not necessarily easy to configure so as to establish interface therebetween and to perform radiation image capturing in cooperation with each other by exchanging signals and such like as described above.
Therefore, in such case, it is necessary to configure so that the radiation image capturing apparatus detects start of radiation irradiation by itself to perform radiation image capturing. Hereinafter, the method of performing radiation image capturing in a state where the radiation image capturing apparatus and the radiation generation apparatus cannot cooperate (or do not cooperate) with each other in such way will be called the non-cooperation method.
After many studies, the inventors of the present invention were able to develop several new detection techniques by which a radiation image capturing apparatus can accurately detect the start of radiation irradiation by itself. It is known that radiation image capturing can be performed accurately even in the non-cooperation method in which signals or such like cannot be exchanged between the radiation image capturing apparatus and the radiation generation apparatus if such new detection techniques are used.
However, on the other hand, for example, it has been known that preferred radiation images cannot be necessarily obtained if the parameter which is set in the radiation image capturing apparatus in a case where radiation image capturing is performed in the conventional cooperation method is applied as it is to a case where such new detection technique is adopted.
When the radiation image capturing apparatus is configured so as to perform radiation image capturing in both of the cooperation method and the non-cooperation method, the negative effect as described above can occur if the parameter in the cooperation method is applied when radiation image capturing is performed in the non-cooperation method. However, on the contrary, if the parameter is changed so as to be appropriate for the non-cooperation method, there can be a negative effect such that the radiation image capturing apparatus and the radiation image capturing system cannot be conveniently used by a radiation technologist, for example, when radiation image capturing is to be performed next in the cooperation method.
For example, in order to reduce electric power consumption in the radiation image capturing apparatus, the configuration may be such that the power consumption mode of the radiation image capturing apparatus can be switched between the image capturing mode in which radiation image capturing can be performed by supplying power to a scan activation unit 15 and each reading circuit 17 (see after-mentioned FIG. 7), by applying reverse bias voltage from a bias power source 14 to each radiation detection element 7 or such like and a sleep mode in which these power supply is stopped and power is supplied only to the necessary function parts such as an antenna device 41. Here, in the sleep mode, the radiation image capturing cannot be performed.
In such case, when the power consumption mode of the radiation image capturing apparatus is switched from the sleep mode to the image capturing mode, as mentioned below, usually, radiation image capturing cannot be carried out immediately after the switching, and the radiation source 52 is allowed to emit radiation onto the radiation image capturing apparatus only after the radiation image capturing apparatus is put on standby for a predetermined time period.
Such elapsed time until the radiation source 52 is allowed to actually emit radiation onto the radiation image capturing apparatus after it becomes possible for the radiation image capturing apparatus to perform radiation image capturing by switching the power consumption mode thereof from the sleep mode to the image capturing mode, by turning on the radiation image capturing apparatus or such like will be called standby time hereinafter.
Standby time for the case where radiation image capturing is performed in the cooperation method may be set in the radiation image capturing apparatus. However, in a case where radiation image capturing is performed in the non-cooperation method, when the radiation image capturing apparatus is put on standby only for the above standby time before carrying out radiation image capturing, drastic difference in brightness may appear in the radiation image as mentioned later.
On the other hand, when the standby time is set so as not to cause the drastic difference in brightness as described above in the case of the non-cooperation method, there is a problem such that when radiation image capturing is carried out in the cooperation method next, the radiation image capturing apparatus and the radiation image capturing system cannot be conveniently used by a radiation technologist because the radiation image capturing apparatus need to be on standby longer than needed.